This project seeks to ascertain the amount and geographic distribution of genetic variation at the DNA level in three Drosophila species at three loci. It also seeks to determine what forces are most important in generating and maintaining the genetic variation in these populations. Understanding the genetic variation with Drosophila species also be applicable to studying human genetic variation. Ten to twenty copies of SOD, ADH, and Gpdh will be sequenced from different localities in D. melanogaster, D. simulans, and D. willistoni. Mutation parameters, migration parameters and recombination parameters will be estimated. The possibility of selectively maintained polymorphisms and recent selective substitutions will be tested by several statistical techniques, using within species variation and between species comparisons of DNA sequences.